Observational study of HR+/HER2− metastatic breast cancer patients treated with abemaciclib in Spain in the Named Patient Use Program (AbemusS)

Introduction/objectives To describe abemaciclib use in patients with hormone receptor-positive, human epidermal growth factor receptor-negative (HR+/HER2−) metastatic breast cancer (mBC) who participated in the Named Patient Use program (NPU) in Spain. Material and methods This retrospective study was based on medical record review of patients across 20 centers during 2018/2019. Patients were followed up until death, enrolment in a clinical trial, loss of follow-up or study end. Clinical and demographic characteristics, treatment patterns and abemaciclib effectiveness were analyzed; time-to-event and median times were estimated using the Kaplan–Meier (KM) method. Results The study included 69 female patients with mBC (mean age 60.4 ± 12.4 years), 86% of whom had an initial diagnosis of early BC and 20% had an ECOG ≥ 2. Median follow-up was 23 months (range 16–28). Metastases were frequently observed in bone (79%) and visceral tissue (65%), with 47% having metastases in > 2 sites. Median number of treatment lines before abemaciclib was 6 (range 1–10). Abemaciclib monotherapy was received by 72% of patients and combination therapy with endocrine therapy by 28% of patients; 54% of patients required dose adjustments, with a median time to first adjustment of 1.8 months. Abemaciclib was discontinued in 86% of patients after a median of 7.7 months (13.2 months for combination therapy and 7.0 months for monotherapy) mainly due to disease progression (69%). Conclusion These results suggest that abemaciclib is effective, as monotherapy and in combination, for patients with heavily pretreated mBC, consistent with clinical trial results.